1. Field of the Invention
This invention relates to an improved apparatus for continuously dissolving gas in a liquid and, more particularly, to a pressurized device to dissolve gas in a liquid.
2. State-of-the-Art
In various wastewater treatment processes, such as the well-known dissolved air flotation process (DAF), it is required that gas be dissolved in a liquid. In a DAF process, such as described in U.S. Pat. No. 3,179,252, gas bubbles are released when a super-atmospheric liquid-gas solution is depressurized in an open tank; the released bubbles then associate with solids in the liquid and carry them to the surface. It should be appreciated that the efficiency of this type of process depends, in part, upon the quantity of pressurized gas which can be dissolved in a given amount of liquid.
One conventional type of dissolving apparatus includes means for contacting a gas and a liquid in a pressurized tank. In this type of device, liquid and compressed gas, usually air, are simultaneously introduced to a pressurized reaction zone. Such devices are based upon the hypothesis that the quantity of gas which can be dissolved in a liquid at a given temperature and pressure depends primarily on the amount of liquid surface area exposed to the gas and on the duration of the gas-liquid contact time. Typically, such devices incorporate a feed nozzle to spray liquid against a splash plate in the reaction zone to create liquid droplets; the droplets then contact, and dissolve gas injected into the reaction zone. A device of this type is taught in U.S. Pat. No. 3,100,810.